Nest studied customers’ heating and cooling savings, and the results are in

In a new white paper, Nest said that based on data it gathered from homeowners from before and after they installed the smart thermostat, the savings averaged out to 10 to 12 percent for heating bills and 15 percent for cooling bills. The company estimates customers saved an average of $131 to $145 a year. The device costs $249, so it would pay for itself in about two years, the company says.

The data came from 735 homes in 36 states for gas usage and 624 homes in 39 states for electric. Only customers who had enrolled in Nest’s MyEnergy service, which lets users track and compare their utility bills, were included in the study. (Back when Google first acquired the thermostat maker, Nest’s CEO had to reassure customers that both companies would be transparent about how they used users’ data.) A control group of non-Nest, MyEnergy customers ensured that energy savings weren’t due to lower energy costs or unseasonably warm weather, for example.

Nest says its internal study is backed up by two independent ones, one from the Energy Trust of Oregon, which found Nest users had 12-percent reductions in electric heating bills, and the other from Indiana utility company Vectren.

“While we always knew that the Nest Learning Thermostat helps people save energy, we now have independent, third-party evidence of how much it can save,” says Ben Bixby, Nest’s general manager of energy services.

Still, the company admits there are lots of factors that will determine how much the device can actually save you. If you live in a temperate climate and already program your thermostat, you probably won’t see the same reduction in your utility bill as someone who leaves the heat blasting all day and night because they’re snowed in from a Nor’easter.